Here is one from Google:
"A locus is the set of all points (usually forming a curve or surface) satisfying some condition. For example, the locus of points in the plane equidistant from a given point is a circle, and the set of points in three-space equidistant from a given point is a sphere."

Locus means the locations/positions of a set of points satisfying some condition.

"locus" ---"location"

And, yes, a locus of points can be a line, a curved line, a surface,.....